1. Field of the Invention
The invention pertains to antennas and multiplexers more particularly to multiplexers for use with antennas and receiving apparatus operating in the AM/FM, CB and television frequency ranges.
2. Prior Art
It is known to use multiband antennas coupled to multiplexers in systems capable of receiving AM/FM and weather band signals and transmitting and receiving CB and cellular phone signals. See, for example, commonly assigned U.S. Pat. No. 6,297,711 to Seward, et al. In recent years, the technology of cellular telephones has progressed to the point where coupling a cellular telephone to a vehicular antenna is unnecessary.
At the same time, there is increased demand to provide television reception in vehicles, particularly in commercial trucking and in marine environments. In the trucking industry, separate “Vee” antennas are typically installed in the headliner of composite bodied trucks, and in the marine industry, similar separate television antennas are used for television reception, apart from the other communication antennas and antennas for conventional AM/FM reception.
There remains a need to minimize the number of antennas in use, and the now unused cellular port in known multiplexers provides a convenient port for a television signal from a multiband antenna. But the solution is not as simple as replacing the cellular port on the multiplexer with a television port. One problem with incorporating television reception on existing multiband antenna systems is that FM frequencies are between television channels 6 and 7, so that splitting like frequencies over two receivers (one FM and one television) reduces the signal to each. In addition, the receivers tend to load the system which results in greater losses and degradation of the signals. The problem of incorporating television reception into existing multiband antenna systems remains.